U.S. patent number 10,538,432 [Application Number 15/603,075] was granted by the patent office on 2020-01-21 for methods of forming graphene-coated diamond particles and polycrystalline compacts.
This patent grant is currently assigned to Baker Hughes, a GE company, LLC. The grantee listed for this patent is Baker Hughes, a GE company, LLC. Invention is credited to Gaurav Agrawal, Soma Chakraborty, Anthony A. DiGiovanni, Vipul Mathur, Danny E. Scott.
United States Patent |
10,538,432 |
Chakraborty , et
al. |
January 21, 2020 |
Methods of forming graphene-coated diamond particles and
polycrystalline compacts
Abstract
Coated diamond particles have solid diamond cores and at least
one graphene layer. Methods of forming coated diamond particles
include coating diamond particles with a charged species and
coating the diamond particles with a graphene layer. A composition
includes a substance and a plurality of coated diamond particles
dispersed within the substance. An intermediate structure includes
a hard polycrystalline material comprising a first plurality of
diamond particles and a second plurality of diamond particles. The
first plurality of diamond particles and the second plurality of
diamond particles are interspersed. A method of forming a
polycrystalline compact includes catalyzing the formation of
inter-granular bonds between adjacent particles of a plurality of
diamond particles having at least one graphene layer.
Inventors: |
Chakraborty; Soma (Houston,
TX), DiGiovanni; Anthony A. (Houston, TX), Agrawal;
Gaurav (Aurora, CO), Scott; Danny E. (Montgomery,
TX), Mathur; Vipul (Houston, TX) |
Applicant: |
Name |
City |
State |
Country |
Type |
Baker Hughes, a GE company, LLC |
Houston |
TX |
US |
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Assignee: |
Baker Hughes, a GE company, LLC
(Houston, TX)
|
Family
ID: |
45994750 |
Appl.
No.: |
15/603,075 |
Filed: |
May 23, 2017 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20170253490 A1 |
Sep 7, 2017 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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14819031 |
Aug 5, 2015 |
9670065 |
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13283021 |
Aug 11, 2015 |
9103173 |
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61408382 |
Oct 29, 2010 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C04B
35/62839 (20130101); E21B 10/567 (20130101); B22F
1/02 (20130101); C22C 26/00 (20130101); B05D
1/36 (20130101); C04B 35/52 (20130101); C04B
35/00 (20130101); B05D 7/5483 (20130101); B05D
7/5883 (20130101); C01B 32/28 (20170801); B22F
1/025 (20130101); B22F 2005/001 (20130101); C04B
2235/427 (20130101); B22F 2998/00 (20130101); B22F
2998/00 (20130101); C22C 26/00 (20130101) |
Current International
Class: |
C01B
32/28 (20170101); B22F 1/02 (20060101); B22F
5/00 (20060101); C04B 35/00 (20060101); E21B
10/567 (20060101); C22C 26/00 (20060101); C04B
35/628 (20060101); B05D 7/00 (20060101); B05D
1/36 (20060101); C04B 35/52 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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101263083 |
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Sep 2008 |
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CN |
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101324175 |
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Dec 2008 |
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CN |
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101428786 |
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May 2009 |
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CN |
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101463472 |
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Jun 2009 |
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CN |
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101469417 |
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Jul 2009 |
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CN |
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101772615 |
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Jul 2010 |
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CN |
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2004040029 |
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May 2004 |
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WO |
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Primary Examiner: Dunn; Colleen P
Assistant Examiner: Christie; Ross J
Attorney, Agent or Firm: TraskBritt
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a divisional of U.S. patent application Ser.
No. 14/819,031, filed Aug. 5, 2015, now U.S. Pat. No. 9,670,065,
issued Jun. 6, 2017, which is a divisional of U.S. patent
application Ser. No. 13/283,021, filed Oct. 27, 2011, now U.S. Pat.
No. 9,103,173, issued Aug. 11, 2015, which application claims the
benefit of U.S. Provisional Patent Application Ser. No. 61/408,382,
filed Oct. 29, 2010, titled "Graphene-Coated Diamond Particles,
Polycrystalline Compacts, Drill Bits, and Compositions of
Graphene-Coated Diamond Particles, and Methods of Forming Same,"
the disclosure of each of which is incorporated herein in its
entirety by this reference. The subject matter of this application
is also related to the subject matter of U.S. patent application
Ser. No. 13/166,557, filed Jun. 22, 2011, now U.S. Pat. No.
8,840,693, issued Sep. 23, 2014.
Claims
What is claimed is:
1. A method of forming a polycrystalline compact, comprising:
forming at least two graphene layers separated by at least one
additional layer of material on each of a first plurality of
diamond particles; and catalyzing the formation of inter-granular
bonds between adjacent particles of the first plurality of diamond
particles.
2. The method of claim 1, further comprising interspersing the
first plurality of diamond particles with a second plurality of
diamond particles.
3. The method of claim 2, wherein the first plurality of diamond
particles has a first average diameter and the second plurality of
diamond particles has a second average diameter different from the
first average diameter.
4. The method of claim 2, further comprising disposing a catalyst
material in interstitial spaces between the first plurality of
diamond particles and the second plurality of diamond
particles.
5. The method of claim 2, wherein at least one of the first
plurality of diamond particles and the second plurality of diamond
particles comprises a plurality of diamond particles having at
least one layer comprising a material selected from the group
consisting of cobalt, iron, nickel, and alloys thereof.
6. The method of claim 2, wherein at least one of the first
plurality of diamond particles and the second plurality of diamond
particles comprises a plurality of diamond particles having at
least one layer comprising magnesium carbonate.
7. The method of claim 2, wherein at least one of the first
plurality of diamond particles and the second plurality of diamond
particles comprises a plurality of diamond particles having at
least one layer comprising a material selected from the group
consisting of ceramics and refractory metals.
8. The method of claim 1, further comprising: providing a first
volume comprising the first plurality of diamond particles;
providing a second volume comprising a second plurality of diamond
particles having at least one graphene layer, wherein the second
plurality of diamond particles has a different average diameter
from an average diameter of the first plurality of diamond
particles; and catalyzing the formation of inter-granular bonds
between adjacent particles of the second plurality of diamond
particles.
9. The method of claim 1, further comprising suspending the first
plurality of diamond particles in a fluid.
10. The method of claim 1, wherein the first plurality of diamond
particles comprises diamond nanoparticles, the method further
comprising mixing the diamond nanoparticles with non-diamond
nanoparticles.
11. The method of claim 10, further comprising nucleating diamond
in situ on the non-diamond nanoparticles.
12. The method of claim 1, wherein forming the at least two
graphene layers on each of a first plurality of diamond particles
comprises coating diamond nanoparticles with the at least two
graphene layers.
13. The method of claim 1, wherein forming the at least one
additional layer on each of the first plurality of diamond
particles comprises at least one process selected from the group
consisting of wet chemistry processes, physical deposition
processes, and chemical deposition processes.
14. The method of claim 1, wherein forming the at least one
additional layer on each of the first plurality of diamond
particles comprises coating the diamond particles in a
fluidized-bed reactor.
15. The method of claim 1, wherein forming the at least one
additional layer on each of the first plurality of diamond
particles comprises coating the diamond particles with at least one
material selected from the group consisting of Group VIII A metals,
carbonates, ceramics, and refractory metals.
16. A method of forming a polycrystalline compact, comprising:
forming a first plurality of coated diamond particles, wherein each
coated diamond particle comprises at least two graphene layers
separated by at least one additional layer comprising a material
selected from the group consisting of cobalt, iron, nickel,
niobium, tantalum, molybdenum, tungsten, rhenium, titanium,
vanadium, chromium, silicon, carbonates, carbides, and oxides; and
subjecting the first plurality of coated diamond particles to a
high-temperature high-pressure process.
17. The method of claim 16, wherein each coated diamond particle
comprises at least two additional layers separated by at least one
graphene layer of the at least two graphene layers.
18. The method of claim 16, subjecting the first plurality of
coated diamond particles to an HTHP process comprises subjecting
the coated diamond particles to a pressure greater than about 5.0
GPa and a temperature greater than about 1,000.degree. C.
19. The method of claim 1, wherein the first plurality of diamond
particles further comprise loose diamond particles.
20. The method of claim 16, wherein the first plurality of diamond
particles further comprise loose diamond particles.
Description
FIELD
Embodiments of the present disclosure relate generally to coated
diamond particles, which may be used in, by way of non-limiting
example, fluid suspensions, polymers, elastomers, polycrystalline
compacts, and earth-boring tools, and to methods of forming such
diamond particles.
BACKGROUND
Diamond crystals are useful in various industrial applications. For
example, diamond grains may be used in surface polishing, in the
manufacture of drill bits, and as conductive filler materials for
polymers and elastomers. Liquid suspensions of diamond grains may
be used for lubrication, thermal management, or grinding.
Cutting elements used in earth-boring tools often include
polycrystalline diamond compact (often referred to as "PDC")
cutting elements, which are cutting elements that include cutting
faces of a polycrystalline diamond material. Polycrystalline
diamond material is material that includes inter-bonded grains or
crystals of diamond material. In other words, polycrystalline
diamond material includes direct, inter-granular bonds between the
grains or crystals of diamond material. The terms "grain" and
"crystal" are used synonymously and interchangeably herein.
Polycrystalline diamond compact cutting elements are formed by
sintering and bonding together relatively small diamond grains
under conditions of high temperature and high pressure in the
presence of a catalyst (for example, cobalt, iron, nickel, or
alloys or mixtures thereof) to form a layer or "table" of
polycrystalline diamond material on a cutting element substrate.
These processes are often referred to as
high-temperature/high-pressure (or "HTHP") processes. The cutting
element substrate may comprise a cermet material (i.e., a
ceramic-metal composite material) such as cobalt-cemented tungsten
carbide. In such instances, the cobalt or other catalyst material
in the cutting element substrate may diffuse into the diamond
grains during sintering and serve as the catalyst material for
forming the inter-granular diamond-to-diamond bonds, and the
resulting diamond table, from the diamond grains. In other methods,
powdered catalyst material may be mixed with the diamond grains
prior to sintering the grains together in an HTHP process. Methods
of forming polycrystalline compacts with interstitial materials are
described in U.S. Patent Application Publication No. 2011/0061942
A1, "Polycrystalline Compacts Having Material Disposed in
Interstitial Spaces Therein, Cutting Elements and Earth-Boring
Tools Including Such Compacts, and Methods of Forming Such
Compacts", published Mar. 17, 2011, the disclosure of which is
incorporated herein in its entirety by this reference.
Upon formation of a diamond table using an HTHP process, catalyst
material may remain in interstitial spaces between the grains of
diamond in the resulting polycrystalline diamond table. The
presence of the catalyst material in the diamond table may
contribute to thermal damage in the diamond table when the cutting
element is heated during use, due to friction at the contact point
between the cutting element and the rock formation being cut.
PDC cutting elements in which the catalyst material remains in the
diamond table are generally thermally stable up to a temperature of
about seven hundred fifty degrees Celsius (750.degree. C.),
although internal stress within the cutting element may begin to
develop at temperatures exceeding about four hundred degrees
Celsius (400.degree. C.) due to a phase change that occurs in
cobalt at that temperature (a change from the "beta" phase to the
"alpha" phase). Also beginning at about four hundred degrees
Celsius (400.degree. C.), there is an internal stress component
that arises due to differences in the thermal expansion of the
diamond grains and the catalyst at the grain boundaries. This
difference in thermal expansion may result in relatively large
tensile stresses at the interface between the diamond grains, and
contributes to thermal degradation of the microstructure when PDC
cutting elements are used in service. Differences in the thermal
expansion between the diamond table and the cutting element
substrate to which it is bonded may further exacerbate the stresses
in the PDC cutting element. This differential in thermal expansion
may result in relatively large compressive and/or tensile stresses
at the interface between the diamond table and the substrate that
eventually lead to the deterioration of the diamond table, cause
the diamond table to delaminate from the substrate, or result in
the general ineffectiveness of the cutting element.
Furthermore, at temperatures at or above about seven hundred fifty
degrees Celsius (750.degree. C.), some of the diamond crystals
within the diamond table may react with the catalyst material
causing the diamond crystals to undergo a chemical breakdown or
conversion to another allotrope of carbon. For example, the diamond
crystals may graphitize at the diamond crystal boundaries, which
may substantially weaken the diamond table. Also, at extremely high
temperatures, in addition to graphite, some of the diamond crystals
may be converted to carbon monoxide and/or carbon dioxide.
In order to reduce the problems associated with differences in
thermal expansion and chemical breakdown of the diamond crystals in
polycrystalline diamond cutting elements, so-called "thermally
stable" polycrystalline diamond compacts (which are also known as
thermally stable products, or "TSPs") have been developed. Such a
thermally stable polycrystalline diamond compact may be formed by
leaching the catalyst material (e.g., cobalt) out from interstitial
spaces between the inter-bonded diamond crystals in the diamond
table using, for example, an acid or combination of acids (e.g.,
aqua regia). A substantial amount of the catalyst material may be
removed from the diamond table, or catalyst material may be removed
from only a portion thereof. Thermally stable polycrystalline
diamond compacts in which substantially all catalyst material has
been leached out from the diamond table have been reported to be
thermally stable up to temperatures of about twelve hundred degrees
Celsius (1,200.degree. C.). It has also been reported, however,
that such fully leached diamond tables are relatively more brittle
and vulnerable to shear, compressive, and tensile stresses than are
non-leached diamond tables. In addition, it is difficult to secure
a completely leached diamond table to a supporting substrate. In an
effort to provide cutting elements having diamond tables that are
more thermally stable relative to non-leached diamond tables, but
that are also relatively less brittle and vulnerable to shear,
compressive, and tensile stresses relative to fully leached diamond
tables, cutting elements have been provided that include a diamond
table in which the catalyst material has been leached from a
portion or portions of the diamond table. For example, it is known
to leach catalyst material from the cutting face, from the side of
the diamond table, or both, to a desired depth within the diamond
table, but without leaching all of the catalyst material out from
the diamond table.
DISCLOSURE
In some embodiments of the disclosure, a coated diamond particle
has a solid core comprising diamond and at least one graphene layer
over at least a portion of the solid core.
A method of forming a coated diamond particle includes coating a
diamond particle with a charged species and coating the diamond
particle with a graphene layer.
In some embodiments, a composition includes a substance and a
plurality of coated diamond particles dispersed within the
substance. Each coated diamond particle has a diamond core and at
least one graphene layer formed or otherwise provided over at least
a portion of the diamond core.
An intermediate structure including a hard polycrystalline material
comprises a first plurality of diamond particles and a second
plurality of diamond particles. At least one of the first plurality
of diamond particles and the second plurality of diamond particles
comprises a plurality of diamond particles having at least one
graphene layer. The first plurality of diamond particles and the
second plurality of diamond particles are interspersed.
A method of forming a polycrystalline compact includes coating each
of a plurality of diamond particles with at least one graphene
layer and catalyzing the formation of inter-granular bonds between
adjacent particles of the plurality of diamond particles.
BRIEF DESCRIPTION OF THE DRAWINGS
While the specification concludes with claims particularly pointing
out and distinctly claiming what are regarded as embodiments of the
disclosure, various features and advantages of embodiments of the
disclosure may be more readily ascertained from the following
description of some embodiments when read in conjunction with the
accompanying drawings, in which:
FIGS. 1 through 4 illustrate embodiments of coated diamond
particles;
FIG. 5 illustrates an embodiment of a polycrystalline diamond
compact;
FIG. 6 is a simplified drawing showing how polycrystalline material
of the polycrystalline diamond compact of FIG. 5 may appear under
magnification, and illustrates inter-bonded larger and smaller
grains of hard material; and
FIG. 7 is a perspective view of an embodiment of a fixed-cutter
earth-boring rotary drill bit that includes a plurality of
polycrystalline diamond compacts like that shown in FIG. 5.
DETAILED DESCRIPTION
The illustrations presented herein are not actual views of any
particular particles, polycrystalline compact, microstructure of
polycrystalline material, or drill bit, and are not drawn to scale,
but are merely idealized representations employed to describe the
present disclosure. Additionally, elements common between figures
may retain the same numerical designation.
As used herein, the term "drill bit" means and includes any type of
bit or tool used for drilling during the formation or enlargement
of a wellbore and includes, for example, rotary drill bits,
percussion bits, core bits, eccentric bits, bicenter bits, reamers,
expandable reamers, mills, drag bits, roller cone bits, hybrid
bits, and other drilling bits and tools known in the art.
As used herein, the term "particle" means and includes any coherent
volume of solid matter having an average dimension of about 2 mm or
less. Grains (i.e., crystals) and coated grains are types of
particles. As used herein, the term "nanoparticle" means and
includes any particle having an average particle diameter of about
500 nm or less. The term "nanodiamond" means and includes
nanoparticles of diamond material, that is, diamond grains having
an average particle diameter of about 500 nm or less. As used
herein, the term "micron diamond" means and includes diamond grains
in a range from about 1 .mu.m to about 500 .mu.m. The term
"submicron diamond" means and includes diamond grains in a range
from about 500 nm to about 1 .mu.m.
The term "polycrystalline material" means and includes any material
comprising a plurality of grains (i.e., crystals) of the material
that are bonded directly together by inter-granular bonds. The
crystal structures of the individual grains of the material may be
randomly oriented in space within the polycrystalline material.
As used herein, the term "inter-granular bond" means and includes
any direct atomic bond (e.g., covalent, metallic, etc.) between
atoms in adjacent grains of material.
As used herein, the term "formed over" means and includes formed
on, over, and/or around a material. A material may be formed over
(that is, on, over, and/or around) another material by depositing,
growing, or otherwise providing a layer of source material on,
over, and/or around the another material. The particular process
used to deposit each layer will depend upon the particular material
composition of that layer, the composition of the another material,
the geometry of the another material and the layer, etc. Many
suitable processes for depositing such layers are known in the art
including, for example, wet chemistry processes (e.g., dip coating,
solid-gel processes, etc.), physical deposition processes (e.g.,
sputtering, also known as physical vapor deposition (PVD), etc.),
and chemical deposition processes (e.g., chemical vapor deposition
(CVD), atomic layer deposition (ALD), etc.), or combinations
thereof. In some embodiments, the layer of source material may be
provided over the another material in a fluidized bed reactor,
which may also be combined with one or more of the aforementioned
techniques.
As used herein, the term "functionalized," when referring to a
surface, means and includes a surface to which a material (i.e., a
functional group) has been added by chemical interaction (e.g.,
bonding). Virtually any organic compound may be added to a surface.
A surface may be functionalized to achieve any desired surface
property, such as hydrophilicity, hydrophobicity, reactivity with
selected chemical species, etc.
FIG. 1 is a simplified cross-section of an embodiment of a coated
diamond particle 100 with a core 102 and an outer layer 106
comprising graphene. The core 102 of the coated diamond particle
100 may comprise micron diamond, submicron diamond, nanodiamond, or
any other diamond particle. The core 102 may be formed by any
method known in the art, such as by a detonation synthesis process,
commonly used to form nanodiamond. A carbon shell 104, which may be
a layer of carbon, commonly referred to in the art as a "carbon
onion", may be formed over the core 102. The carbon shell 104 may
be formed during the formation of the core 102 or by heating the
core 102 to a high temperature for a period of time in which an
outer shell of the core 102 may change from a crystalline structure
to a non-crystalline structure. For example, the core 102 may be
heated to more than about 800.degree. C., for more than about 30
minutes. The carbon shell 104 may be graphite or a graphene-based
structure. The carbon shell 104 may provide reactive sites to which
the outer layer 106 may attach.
The surface of the carbon shell 104 may be chemically modified by
coating it with a charged species, such as a positively charged
amine-terminated group (e.g., a branched-polyethyleneimine
(B-PEI)). The carbon shell 104 may then be immersed in a solution
containing an oppositely charged species (e.g., a polyacrylic acid
or a negatively charged graphene entity). The charged species may
be a transient coating, configured to enable adherence of graphene
layers 108. In some embodiments, the charged species may be a
permanent coating that becomes integrated into outer layer 106.
In some embodiments, shown as coated diamond particle 101 in FIG.
2, the carbon shell 104 may be omitted. The surface of the core 102
may be chemically modified by attaching a reactive group to the
core 102, such as an acid group, an epoxy group, a hydroxyl group,
etc. The reactive group may provide reactive sites or anchors to
which the outer layer 106 may attach.
An outer layer 106 may be formed over the core 102 or the carbon
shell 104 (FIG. 1). The outer layer 106 may comprise graphene
layers 108. The first graphene layer 108 (i.e., the graphene layer
with the smallest inside diameter) may be formed over the core 102
or the carbon shell 104, and each successive graphene layer 108 may
be formed over a previously formed graphene layer 108. The coated
diamond particle 100 or 101 may be chemically modified by coating
it with a charged species. The coated diamond particle 100 or 101
may then optionally be immersed in a solution containing an
oppositely charged species. A graphene layer 108 may then be formed
over the charged species or over the oppositely charged species on
the surface of the coated diamond particle 100 or 101. The graphene
layer 108 may be positively charged, negatively charged, or
uncharged. The process may be repeated any number of times, with
graphene layers 108 being formed over a core 102, a carbon shell
104, previously formed graphene layers 108, and/or a charged
species. Methods of forming graphene layers on substrates are
described in U.S. Patent Application Publication No. 2011/0200825
A1, titled "Nano-Coatings for Articles", published Aug. 18, 2011,
the disclosure of which is incorporated herein in its entirety by
this reference. The methods described therein may be used as
described herein to apply graphene layers to particles. Methods of
depositing nanodiamond layer-by-layer onto diamond particles have
been described in Gaurav Saini et al., Core-Shell Diamond as a
Support for Solid-Phase Extraction and High-Performance Liquid
Chromatography, 82 ANAL. CHEM. 4448-56 (2010), the disclosure of
which is incorporated herein in its entirety by this reference.
In some embodiments, outer layer 106 may be formed over only a
portion of the carbon shell 104, or over only a portion of the core
102. In such embodiments, a partially coated diamond particle may
be formed. In other embodiments, some graphene layers 108 may be
formed over the entire carbon shell 104 or core 102, while others
may be formed over only a portion of the carbon shell 104 or core
102.
Multiple graphene layers 108 may be formed such that the coated
diamond particle 100 or 101 exhibits selected values for one or
more selected physical properties, such as diameter, thickness of
outer layer 106, electrical conductivity, thermal conductivity,
mechanical strength, coefficient of thermal expansion, wettability,
mass, geometry, surface energy, specific surface area, etc. For
example, the specific surface area of coated diamond particles 100
or 101 may be from about 10 m.sup.2/g to about 2200 m.sup.2/g (as
determined by, e.g., a gas adsorption measurement). Coated diamond
particles 100 or 101 may have the unique features associated with
diamond particles, such as hardness and thermal conductivity, plus
features of a graphene coating, such as wettability. When the
coated diamond particles 100 or 101 are used in suspensions or
solids, the coated diamond particles 100 or 101 may change some
physical properties of the suspensions or solids. For example, the
thermal conductivity, mechanical strength, and electrical
conductivity of a fluid or solid may be increased by suspending
graphene-coated diamond particles therein.
Features such as wettability may be particularly valuable in
liquids, such as lubricating oils. High thermal conductivity may be
an important feature for oils used in motors and pumps because, in
such applications, heat must be removed from operating components.
Diamond particles in suspension, with their high thermal
conductivity, may therefore be an attractive additive.
Unfortunately, uncoated diamond particles may settle quickly from
oil, because diamond has poor wettability in oil. Rapid settling
may make diamond grains impractical for use in oils because the
grains must be redispersed to ensure proper lubrication. In pumps
and motors, there may be no convenient way to effect such
redispersion before startup. Graphene may limit the settling
problem because if properly functionalized, it may have higher
wettability in oil than diamond does. By coating diamond grains
with graphene, the beneficial features of both materials may be
combined. It may be possible to keep coated diamond particles 100
or 101 in suspension much longer than uncoated diamond particles.
Because they may remain in suspension, coated diamond particles 100
or 101 may be used effectively to increase the thermal conductivity
and lubricating properties of the oil.
Coated diamond particles 100 or 101 may also be used for polishing.
Diamond crystals have properties that may be beneficial for
polishing, such as hardness, thermal conductivity, and durability,
but poor wettability may cause uncoated crystals to settle.
Functionalized graphene coatings may increase wettability of
diamond crystals in polishing liquids, promoting more uniform
polishing.
Wettability may also be beneficial in polymers and elastomers.
Polymers and elastomers may benefit from higher thermal
conductivity of diamond grains. Diamond grains tend to settle
quickly from uncured polymers and elastomers, making it difficult
to form a cured product containing a generally uniform distribution
of the diamond grains. Functionalized graphene-coated diamond
grains, on the other hand, may remain in suspension while the
polymer or elastomer cures, resulting in a solid with diamond
grains dispersed uniformly throughout. The thermal conductivity,
mechanical strength, and electrical conductivity of the polymer or
elastomer may be increased through the addition of graphene-coated
diamond particles.
Diamond grains may be used to form cutting elements. For example,
as discussed with reference to FIG. 5 below, polycrystalline
compacts may be formed by sintering hard polycrystalline materials,
including diamond grains having graphene coatings. To aid bonding
of diamond grains in the sintering process, catalysts or other
materials may be added among the grains. Coated diamond particles
may be used in the formation of polycrystalline compacts. In some
embodiments, the coated diamond particles comprise one or more
additional layers of materials other than graphene for use in a
sintering process.
FIG. 3 is a simplified cross section of an embodiment of a coated
diamond particle 120 comprising at least one additional layer 110.
Coated diamond particle 120 may, like the coated diamond particle
100 shown in FIG. 1, have a core 102 and a carbon shell 104. The
carbon shell 104 may optionally be omitted, as in coated diamond
particle 121, shown in FIG. 4. Coated diamond particle 120 or 121
may further comprise an outer layer 112 having one or more graphene
layers 108 and one or more additional layers 110. The outer layer
112 of the coated diamond particle 120 or 121 may comprise
alternating graphene layers 108 and additional layers 110. In some
embodiments, the additional layers 110 may comprise materials that
are catalytic or partially catalytic to diamond synthesis. For
example, an additional layer 110 may comprise a Group VIII A
element (e.g., iron, cobalt, or nickel) or an alloy thereof. In
additional embodiments, the additional layer 110 may comprise a
carbonate material, such as a carbonate of one or more of
magnesium, calcium, strontium, and barium. The additional layer 110
may comprise other high-temperature/high-pressure nonmetallic
diamond catalysts, such as silicon. In certain embodiments, an
additional layer 110 may be a high-pressure activated catalyst such
as magnesium carbonate. In various embodiments, an additional layer
110 may be a protective coating of ceramic or refractory metal.
Some additional layers 110 may enhance sustainability of the coated
diamond particles 120 or 121 in a sintering cycle so that coated
diamond particles 120 or 121 may remain in their initial state or
participate in the HTHP reaction at a later processing stage.
The outer layer 112 of the coated diamond particle 120 may be
formed over the carbon shell 104. In embodiments of coated diamond
particles 121 without a carbon shell 104, the outer layer may be
formed directly over the core 102. The first layer of the outer
layer 112 (i.e., the layer with the smallest inside diameter) may
be a graphene layer 108 or an additional layer 110, and may be
formed over the core 102 or carbon shell 104. Each successive layer
108 or 110 may be formed over a previously formed layer 108 or 110.
Before forming each graphene layer 108 or additional layer 110 over
the coated diamond particle 120 or 121, the coated diamond particle
120 or 121 may be chemically modified by coating it with a charged
species, such as those described with reference to the coated
diamond particle 100 of FIG. 1. The coated diamond particle 120 or
121 may then be immersed in a solution containing an oppositely
charged species. Multiple graphene layers 108 and/or multiple
additional layers 110 may be formed such that the coated diamond
particle 120 or 121 exhibits a selected physical property, such as
diameter, thickness of outer layer 112, electrical conductivity,
thermal conductivity, mechanical strength, coefficient of thermal
expansion, wettability, mass, geometry surface energy, specific
surface area, etc. Functionalized graphene-coated diamond grains
may mix more fully with micron diamond. Furthermore, graphene
layers 108 may provide a source of carbon to aid the sintering
process.
Additional layers 110 may be formed by depositing, growing, or
otherwise providing a layer of material. The particular process
used to deposit each additional layer 110 may depend upon the
particular material composition of that additional layer 110, the
composition of the material over which it is formed, the geometry
of the material over which it is formed, etc. Many suitable
processes for depositing such layers are known in the art
including, for example, wet chemistry processes (e.g., dip coating,
solid-gel processes, etc.), physical deposition processes (e.g.,
PVD) and chemical deposition processes (e.g., CVD, ALD, etc.). In
some embodiments, the additional layer 110 may be formed in a
fluidized-bed reactor.
In some embodiments, the graphene layers 108 may alternate with the
additional layers 110. That is, a graphene layer 108 may be formed
over the core 102 or carbon shell 104, and an additional layer 110
may be formed over the graphene layer 108. A second graphene layer
108 may be formed over the additional layer 110, and a second
additional layer 110 may be formed over the second graphene layer
108. This sequence may continue for any number of layers.
Alternatively, an additional layer 110 may be formed over the core
102 or carbon shell 104, and a graphene layer 108 may be formed
over the additional layer 110. A second additional layer 110 may be
formed over the graphene layer 108, and a second graphene layer 108
may be formed over the second additional layer 110. This sequence,
too, may continue for any number of layers.
In other embodiments, multiple graphene layers 108 may be formed
sequentially, with additional layers 110 interspersed in patterns
other than alternating. For example, two, three, four, etc.,
graphene layers 108 may be formed over the core 102 or carbon shell
104, followed by an additional layer 110. Two, three, four, etc.,
additional graphene layers 108 may be formed, followed by another
additional layer 110. The sequence may continue for any number of
layers.
As an additional example, two, three, four, etc., additional layers
110 may be formed over the core 102 or carbon shell 104, followed
by a graphene layer 108. Two, three, four, etc., additional layers
110 may be formed, followed by another graphene layer 108. The
sequence may continue for any number of layers.
Similarly, two, three, four, etc., additional layers 110 may be
formed over the core 102 or carbon shell 104, followed by two,
three, four, etc., graphene layers 108. Two, three, four, etc.,
additional layers 110 may be formed, followed by another two,
three, four, etc., graphene layers 108. The sequence may continue
for any number of layers, and the sequence may begin with graphene
layers 108 instead of additional layers 110. Furthermore, the
number of each type of layer need not form any recognizable
pattern. For example, a single graphene layer 108 could be formed
over the core 102 or carbon shell 104, and two, three, four, etc.,
additional layers 110 could be formed over the graphene layer 108.
Two, three, four, etc., additional graphene layers 108 could be
formed over the two, three, four, etc., additional layers 110. A
single additional layer 110 could be formed over the two, three,
four, etc., additional graphene layers 108.
Additional layers 110 need not have the same composition as other
additional layers 110. In certain embodiments, two or more
additional layers 110 have distinct compositions. For example, a
first additional layer 110 may comprise a metal such as cobalt,
iron, nickel, or an alloy thereof. A second additional layer 110
may be a high-pressure-activated catalyst such as magnesium
carbonate. A third additional layer 110 may be a protective layer
of ceramic (e.g., carbides, oxides, etc.) or refractory metal
(e.g., Nb, Ta, Mo, W, Re, Ti, V, Cr, etc.). In other embodiments, a
first additional layer 110 and a second additional layer 110 may
comprise the same materials, but the materials may have different
concentrations in each additional layer 110. In short, layers 108
and 110 may be arranged in any combination, configuration, or
order, and additional layers 110 may have compositions identical to
or different from other additional layers 110 within the outer
layer 112.
Due to diamond grains' high strength, the availability of a carbon
source in graphene layers 108, and the processing benefits of
additional layers 110, coated diamond particles 120 or 121 may be
particularly advantageous in the production of cutting elements of
earth-boring tools.
FIG. 5 is a simplified drawing illustrating an embodiment of a
polycrystalline compact 130 of the present disclosure that may be
formed from graphene-coated diamond particles 100, 101, 120, and/or
121. The polycrystalline compact 130 includes a table or layer of
hard polycrystalline material 132 that has been provided on (e.g.,
formed on or secured to) a surface of a supporting substrate 134.
In additional embodiments, the polycrystalline compact 130 may
simply comprise a volume of the hard polycrystalline material 132
having any desirable shape. The hard polycrystalline material 132
may be formed from coated diamond particles 100, 101, 120, and/or
121, described above with reference to FIGS. 1 through 4.
FIG. 6 is an enlarged, schematic view illustrating how a
microstructure of the hard polycrystalline material 132 of the
polycrystalline compact 130 may appear under magnification. As
shown in FIG. 6, the grains of the hard polycrystalline material
132 may have a multimodal (e.g., a bimodal, a trimodal, etc.) grain
size distribution. In other embodiments (not shown), the grain size
distribution may be monomodal. In multimodal grain size
distributions, the hard polycrystalline material 132 may include a
first plurality of grains 136 of hard material having a first
average grain size, and at least a second plurality of grains 138
of hard material having a second average grain size that differs
from the first average grain size of the first plurality of grains
136. In some embodiments, the hard polycrystalline material 132 may
include a third plurality of grains (not shown) of hard material, a
fourth plurality of grains (not shown) of hard material, etc.
Polycrystalline compacts formed from multimodal distributions of
grains are described more fully in U.S. Patent Application
Publication No. 2011/0031034 A1, titled "Polycrystalline Compacts
Including In-Situ Nucleated Grains, Earth-Boring Tools Including
Such Compacts, and Methods of Forming Such Compacts and Tools,"
published Feb. 10, 2011, and in U.S. patent application Ser. No.
13/208,989, now U.S. Pat. No. 8,985,248, issued Mar. 24, 2015,
titled "Cutting Elements Including Nanoparticles in at Least One
Portion Thereof, Earth Boring Tools Including Such Cutting
Elements, and Related Methods," filed Aug. 12, 2011, the disclosure
of each of which is incorporated herein in its entirety by this
reference. Embodiments described therein may be practiced using the
coated diamond particles 100, 101, 120, and/or 121. As a
non-limiting example, a PDC cutting element may have two or more
layers, and each layer may comprise one or more of coated diamond
particles 100, 101, 120, and/or 121. In such embodiments, the two
or more layers may comprise coated diamond particles 100, 101, 120,
and/or 121 of differing sizes and/or compositions.
In the examples that follow, though only two pluralities of grains
136 and 138 are discussed, additional pluralities of grains may be
used. As one example, the first plurality of grains 136 may be
formed from coated diamond particles 120 or 121 formed from
nanodiamond cores 102, and the second plurality of grains 138 may
be formed from coated diamond particles 120 or 121 formed from
micron diamond cores 102. Thus, the first plurality of grains 136
may be formed from nanoparticles used to form the microstructure of
the hard polycrystalline material 132.
A large difference between the average grain size of the first
plurality of grains 136 and the average grain size of the second
plurality of grains 138 may result in smaller interstitial spaces
or voids within the microstructure of the hard polycrystalline
material 132 (relative to conventional polycrystalline materials),
and the total volume of the interstitial spaces or voids may be
more evenly distributed throughout the microstructure of the hard
polycrystalline material 132 (relative to conventional
polycrystalline materials). As a result, any material that might be
present within the interstitial spaces (such as material of
additional layers 110 formed over nanodiamond cores 102) may also
be more evenly distributed throughout the microstructure of the
hard polycrystalline material 132 within the relatively smaller
interstitial spaces therein.
In some embodiments, the hard polycrystalline material 132 may
include a catalyst material 140 (shaded black in FIG. 6) disposed
in interstitial spaces between the first plurality of grains 136
and the second plurality of grains 138. The catalyst material 140
may comprise a catalyst capable of forming (and used to catalyze
the formation of) inter-granular bonds between the first plurality
of grains 136 and the second plurality of grains 138 of the hard
polycrystalline material 132. In other embodiments, however, the
interstitial spaces between the first plurality of grains 136 and
the second plurality of grains 138 in some regions of the hard
polycrystalline material 132, or throughout the entire volume of
the hard polycrystalline material 132, may be at least
substantially free of such a catalyst material 140. In such
embodiments, the interstitial spaces may comprise voids filled with
gas (e.g., air), or the interstitial spaces may be filled with
another material that is not a catalyst material and that will not
contribute to degradation of the polycrystalline material 132 when
the compact 130 is used in a drilling operation.
The catalyst material may be formed of materials that may be
included in one or more additional layers 110. For example, the
catalyst material 140 may comprise a Group VIII A element or an
alloy thereof, and the catalyst material 140 may comprise between
about 0.1% and about 20% by volume of the hard polycrystalline
material 132. In additional embodiments, the catalyst material 140
may comprise a carbonate material, such as a carbonate of one or
more of magnesium, calcium, strontium, and barium. Carbonates may
also be used to catalyze the formation of polycrystalline
diamond.
The hard polycrystalline material 132 of the compact 130 may be
formed using an HTHP process. Such processes, and systems for
carrying out such processes, are generally known in the art and not
described in detail herein. In accordance with some embodiments of
the present disclosure, the first plurality of grains 136 may be
nucleated in situ during the HTHP process used to form the hard
polycrystalline material 132, as described in U.S. Patent
Application Publication No. 2011/0031034 A1, previously
incorporated by reference. In embodiments in which the first
plurality of grains 136 is formed from coated diamond particles
100, 101, 120, and/or 121, graphene layers 108 may act as
carbon-rich centers, and, optionally, additional layers 110 may
catalyze in situ diamond formation during HTHP processing.
In some embodiments, the hard polycrystalline material 132 may be
formed over a supporting substrate 134 (as shown in FIG. 5) of
cemented tungsten carbide or another suitable substrate material in
a conventional HTHP process of the type described, by way of
non-limiting example, in U.S. Pat. No. 3,745,623, titled "Diamond
Tools for Machining," issued Jul. 17, 1973, or may be formed as a
freestanding polycrystalline compact (i.e., without the supporting
substrate 134) in a similar conventional HTHP process as described,
by way of non-limiting example, in U.S. Pat. No. 5,127,923, titled
"Composite Abrasive Compact Having High Thermal Stability," issued
Jul. 7, 1992, the disclosure of each of which is incorporated
herein in its entirety by this reference. In some embodiments, the
catalyst material 140 may be supplied from the supporting substrate
134 during an HTHP process used to form the hard polycrystalline
material 132. For example, the substrate 134 may comprise a
cobalt-cemented tungsten carbide material. The cobalt of the
cobalt-cemented tungsten carbide may serve as the catalyst material
140 during the HTHP process. In some embodiments, the catalyst
material 140 may be supplied by one or more additional layers 110
of coated diamond particles 120 or 121. In other words, one or more
additional layers 110 of coated diamond particles 120 or 121 may
comprise the catalyst material 140.
To form the hard polycrystalline material 132 in an HTHP process, a
particulate mixture comprising grains of hard material, such as
coated diamond particles 100, 101, 120, and/or 121, described with
reference to FIGS. 1 through 4, may be subjected to elevated
temperatures (e.g., temperatures greater than about 1,000.degree.
C.) and elevated pressures (e.g., pressures greater than about 5.0
gigapascals (GPa)) to form inter-granular bonds between the
particles, thereby forming the hard polycrystalline material 132.
Coated diamond particles 100, 101, 120, and/or 121 may provide
graphene layers 108 as a source of carbon, which may promote
enhanced sintering of diamond-to-diamond bonds. Coated diamond
particles 100, 101, 120, and/or 121 may be used in conjunction with
the methods described in U.S. Patent Application Publication No.
2011/0031034 A1, previously incorporated by reference.
Specifically, various non-diamond nanoparticles may act as a source
for diamond nucleation in situ under the appropriate sintering
conditions. In some embodiments, the particulate mixture may be
subjected to a pressure greater than about six gigapascals (6.0
GPa) and a temperature greater than about 1,500.degree. C. in the
HTHP process.
The overall polycrystalline microstructure that may be achieved in
accordance with embodiments of the present disclosure may result in
polycrystalline diamond compacts that exhibit improved durability,
conductivity, and/or thermal stability.
Polycrystalline compacts that embody teachings of the present
disclosure, such as the polycrystalline compact 130 illustrated in
FIG. 5, may be formed and secured to drill bits for use in forming
wellbores in subterranean formations. As a non-limiting example,
FIG. 7 illustrates a fixed-cutter type earth-boring rotary drill
bit 150 that includes a plurality of polycrystalline compacts 130
as previously described herein. The rotary drill bit 150 includes a
bit body 152, and the polycrystalline compacts 130, which serve as
cutting elements, are bonded to the bit body 152. The
polycrystalline compacts 130 may be brazed or otherwise secured
within pockets formed in the outer surface of the bit body 152.
Polycrystalline compacts that embody teachings of the present
disclosure may be formed and secured to any other type of
earth-boring tool for use in forming wellbores in subterranean
formations.
Additional non-limiting example embodiments of the disclosure are
described below.
Embodiment 1
A coated diamond particle comprising a solid core comprising
diamond, and at least one graphene layer over at least a portion of
the solid core.
Embodiment 2
The coated diamond particle of Embodiment 1, further comprising at
least one additional layer formed over at least a portion of the
solid core.
Embodiment 3
The coated diamond particle of Embodiment 2, wherein the at least
one graphene layer comprises two or more graphene layers separated
by the at least one additional layer.
Embodiment 4
The coated diamond particle of Embodiment 2, wherein the at least
one additional layer comprises two or more additional layers
separated by the at least one graphene layer.
Embodiment 5
The coated diamond particle of any of Embodiment 1 through
Embodiment 4, further comprising a carbon shell.
Embodiment 6
The coated diamond particle of any of Embodiment 1 through
Embodiment 5, wherein the coated diamond particle has a diameter of
about 500 nm or less.
Embodiment 7
A method of forming a coated diamond particle, comprising coating a
diamond particle with a charged species and coating the diamond
particle with a graphene layer.
Embodiment 8
The method of Embodiment 7, further comprising coating the diamond
particle with a material selected from the group consisting of
group VIII A elements and alloys thereof.
Embodiment 9
The method of Embodiment 7, further comprising immersing the
diamond particle in a solution comprising an oppositely charged
species before coating the diamond particle with a graphene
layer.
Embodiment 10
A composition comprising a substance and a plurality of coated
diamond particles dispersed within the substance. Each coated
diamond particle has a diamond core and at least one graphene layer
formed over at least a portion of the diamond core.
Embodiment 11
The composition of Embodiment 10, wherein the substance comprises a
fluid. The coated diamond particles are suspended in the fluid.
Embodiment 12
The composition of Embodiment 10, wherein the substance comprises a
solid material. The coated diamond particles are dispersed
throughout the solid material.
Embodiment 13
An intermediate structure including a hard polycrystalline material
comprising a first plurality of diamond particles and a second
plurality of diamond particles. At least one of the first plurality
of diamond particles and the second plurality of diamond particles
comprises a plurality of diamond particles having at least one
graphene layer. The first plurality of diamond particles and the
second plurality of diamond particles are interspersed.
Embodiment 14
The intermediate structure of Embodiment 13, wherein the first
plurality of diamond particles has a first average diameter and the
second plurality of diamond particles has a second average diameter
different from the first average diameter.
Embodiment 15
The intermediate structure of Embodiment 13 or Embodiment 14,
further comprising a catalyst material disposed in interstitial
spaces between the first plurality of diamond particles and the
second plurality of diamond particles.
Embodiment 16
The intermediate structure of any of Embodiment 13 through
Embodiment 15, wherein at least one of the first plurality of
diamond particles and the second plurality of diamond particles
comprises a plurality of diamond particles having at least one
layer comprising a material selected from the group consisting of
cobalt, iron, nickel, and alloys thereof.
Embodiment 17
The intermediate structure of any of Embodiment 13 through
Embodiment 16, wherein at least one of the first plurality of
diamond particles and the second plurality of diamond particles
comprises a plurality of diamond particles having at least one
layer comprising magnesium carbonate.
Embodiment 18
The intermediate structure of any of Embodiment 13 through
Embodiment 17, wherein at least one of the first plurality of
diamond particles and the second plurality of diamond particles
comprises a plurality of diamond particles having at least one
layer comprising a material selected from the group consisting of
ceramics and refractory metals.
Embodiment 19
The intermediate structure of any of Embodiment 13 through
Embodiment 18, further comprising a first layer and a second layer.
The first layer and the second layer each comprise a plurality of
diamond particles having at least one graphene layer. The plurality
of diamond particles of the first layer has a different average
diameter from an average diameter of the plurality of diamond
particles of the second layer.
Embodiment 20
A method of forming a polycrystalline compact, comprising coating
each of a plurality of diamond particles with at least one graphene
layer and catalyzing the formation of inter-granular bonds between
adjacent particles of the plurality of diamond particles.
Embodiment 21
The method of Embodiment 20, further comprising coating each of the
plurality of diamond particles with at least one additional
layer.
The foregoing description is directed to particular embodiments for
the purpose of illustration and explanation. It will be apparent to
one skilled in the art that many modifications and changes to the
embodiments set forth above are possible without departing from the
scope of the embodiments disclosed herein as hereinafter claimed,
including legal equivalents. It is intended that the following
claims be interpreted to embrace all such modifications and
changes.
* * * * *
References